The current proposal deals with the mechanisms and characterization of gonadal oxidases. In particular, 17, 20-lyase and 17alpha-hydroxylase are being studied. Past work has revealed that both enzymes are associated with cytochrome P-450 and its flavoprotein reductase. These microsomal components are embedded in a phospholipid matrix. Partial purification of these components has already been achieved and reconstitution has restored enzyme activity. Further studies of the substrate binding site of P-450 will also be conducted.